When coated abrasives are made from conventional binders such as hide glue, varnish or phenolic resins, the manufacturing process can be both energy-intensive and time-consuming. For example, the widely-used phenolic binders must be dried at high temperatures for long times (e.g., at least about 2 hours at 90.degree. C. (195.degree. F.) for cure of phenolic size coatings). In an effort to reduce energy consumption and increase throughput, coated abrasive manufacturers have investigated electron-beam ("E-beam")-curable binders and photochemically-curable binders, e.g., as described in recently-issued U.S. Pat. Nos. 4,642,126 and 4,652,274.
A general shortcoming of radiation curing as applied to coated abrasive manufacture lies in the inherent difficulty of curing behind an abrasive grain in highly-filled or thick-section coated abrasive products. As a result, the abrasive grains may be poorly adhered on the backing, with concomitant poor product performance. Combinations of E-beam cure and thermally-initiated cure have been employed to overcome this shortcoming; however, such an approach still represents a compromise solution that can require considerable time and energy for completion of a thermal cure cycle.
Aryliodonium salts have been previously described for use as photoinitiators in addition-polymerizable compositions. References relating to such compositions include U.S. Pat. Nos. 3,729,313, 3,741,769, 3,808,006, 4,228,232, 4,250,053 and 4,428,807; H. J. Timpe and H. Baumann, Wiss. Z. Tech. Hochsch. Leuna-Merseburg, 26, 439 (1984); H. Baumann, B. Strehmel, H. J. Timpe and U. Lammel, J. Prakt. Chem, 326 (3), 415 (1984); and H. Baumann, U. Oertel and H. J Timpe, Euro Polym. J., 22 (4), 313 (April 3, 1986).
Mono- and di-ketones have also previously been described for use as photoinitiators in addition-polymerizable compositions. References relating to such compositions include U.S. Pat. Nos. 3,427,161, 3,756,827, 3,759,807 and 4,071,424; U.K. Pat. Specification No. 1,304,112; European Published Pat. Appl. No. 150,952 and Chem. Abs. 95:225704U.